This application claims the priority of German Patent Application No. 100 08 991.7, filed in Germany, Feb. 25, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a gas exchange valve control for internal combustion engines with an electromagnetic actuator, equipped with gas springs. In this device an armature, which is drive-connected to the gas exchange valve, is arranged so as to oscillate between stroke-separated switching magnets against reset forces of the gas springs. The gas springs, separated by the armature, serving as the separating piston, serve to adjust the adapted spring characteristics by the gas metering valves and gas outlet valves, controlled as a function of the load areas of the internal combustion engine. Furthermore, they serve to damp the stop of the separating piston or the armature on the respective switching magnet.
Such an armature is the object of the German patent application P 100 03 116. Its goal is to achieve variably adapted spring characteristics as a function of the load areas of the internal combustion engine by means of a simple construction. Furthermore, the goal is also to achieve a controlled damping of the stop irrespective of the respective spring characteristic.
In this actuator the outer periphery of the armature, serving as the separating piston between the two gas springs, is equipped with a sliding seal, which is friction-connected to the wall of the armature stroke space. Furthermore, the switching magnets are not designed with respect to optimal magnetic line flux.
The invention is based on the problem of improving this class of actuator both with respect to its mechanical construction and its electromagnetic design so that the cost of energy is reduced and the armature is attracted with increased magnetic force.
This problem is solved according to preferred embodiments of the invention in that the armature is designed without any sliding seal and separates the gas springs. In the respective holding position on a switching magnet the armature defines a damping chamber by means of an intercalated elastomeric element. Furthermore, each switching element exhibits a coil in a core, which is laminated centrosymmetrically relative to a guide shaft of the armature or the gas exchange valve. Each core is designed on the outer periphery flush with a coil, arranged in a peripheral groove bordering the armature-sided face, so as to rest planarly against a yoke, enclosing the switching magnets, including the armature stroke space, and which carries essentially in the center between the switching magnets a mechanism which brings about an increased acceleration force at the armature in the respective holding position.
A goal of the mechanical construction of the design of the invention is to provide in the armature stroke space an armature that separates the gas springs without friction owing to the dispensing of a sliding ring seal and to which is assigned, to achieve an air-damped stop, a damping chamber defined by an elastic element. Since there is no armature friction, the cost of energy is advantageously reduced. Furthermore, the damping chamber of the invention achieves in another advantageous manner that the actuator is acoustically improved.
With the electromagnetic design of the actuator according to the invention, a shorter magnetic circuit for each switching magnet is achieved. Thus, with the reduced magnetic circuit at least in the starting phase of the acceleration of the armature from the holding position on one of the switching magnets, the magnetic resistance in the magnetic circuit is significantly reduced by just an air slit. Thus, independently of the applied gas pressure at the armature, the acceleration of said armature can be increased, a feature that is advantageous in an advantageous manner in particular to achieve high speeds of the internal combustion engine. In connection with the shortened magnetic circuit of each switching magnet, according to the invention, it is especially advantageous that their cores be laminated centrosymmetrically in order to reduce the leakage losses or to reduce the vortex losses, as described and illustrated, for example, in the German Patent Document DE 35 00 530 A1.
With the inventive combination of an improved mechanical construction with an improved electromechanical design of a pneumatic, electromagnetic actuator a gas exchange valve control for internal combustion engines of high efficiency is achieved in an advantageous manner. In this respect it is significantly simpler with the electromagnetic potential of the invention to achieve a load-dependent tuning of the pneumatic system.
Advantageous designs of the invention are described herein and in the claims.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.